Using satellite view, it turned out that this is in the middle of a dune near Katwijk.
The area where this spot is located looked fenced from the streets. However using the nearby
entrance to the forest, one would be able to walk up north, using small paths through the dunes.

When I arrived at the forest, it turned out to be not just a forest, but some kind of family attraction.
It is a recreational area which contains a forest, park, playground, etc.
Also, there's a restaurant where you can eat pancakes.

After I parked my car and walked into the forest for 20m, I was confronted with
a sign, telling I should buy a ticket from the machine to get access.
Normally you can just walk around the machine, as it is not blocking the entrance.
However, today the machine was broken, and there was a guy in a small cabin
next to it, selling entrance tickets.

So, I bought a ticket for 1,50 euro.

Then it was a 1,2km walk up to the north to reach the geohash. After a few 100 metres, I was able to
leave the forest and walk through the dunes. The narrow paths were clearly visible
on the satellite view, so I started following those. After 500m, I expected to
walk the path straight up to the geohash. However, there was a sign 'personnel only', entrance
prohibited.
So I decided to try to avoid this path by walking a large circle around it. This would be another
1km walk. But after completing half the circle, the roads were blocked again.

Then I stepped over some barb wire to climb up a hill and try to reach the personnel path
anyway. However the bushes were to dense and I climbed back to the normal path.
Then I went back to the path where I found the first personnel only sign. There was
nobody around so I decided to go for it. After a few 100m though, there was a wooden fence
with a lock. I could climb over it, but the road ended there as well so then I had to manouevre myself through
some thick trees and bushes. I'm not Tarzan and it was getting late so I decided this one is unreachable and this is the
closest you could get.